(1) Technical Field
This invention relates to freezing temperature indicators which will indicate the presence of ice in a water or any aqueous solution having a predetermined freezing temperature.
(2) Description of the Prior Art
An ice detecting system for use in a refrigerated tank in which milk or another liquid is chilled is disclosed in U.S. Pat. No. 2,632,308 and consists of a pair of metallic plates positioned in the tank in spaced relation and connected with a source of electrical current arranged so that the current flows through the milk in the tank until such time as the water in the milk freezes on the plates acting to interupt or lessen the current flow.
U.S. Pat. No. 3,896,278 discloses a device which uses ice to maintain an electrical circuit in open condition, thawing of the ice permitting a conductive element to move to engage a pair of terminals in an alarm circuit so as to complete a circuit therethrough.
U.S. Pat. No. 4,011,552 discloses a temperature sensor incorporating a sensing element such as a thermistor in a closed capsule filled with a liquid that will freeze at a predetermined termperature and connected in an alarm signaling circuit.
The present invention differs substantially from these prior art devices in that the freezing temperature indicator can be of any length so as to supervise any desired area including piping and operates on the novel concept of utilizing an elongated freezable liquid conductor capable of sensing ice formation anywhere along its length and by incorporating sophisticated circuitry can determine the location of the ice in the elongated freezing temperature indicator if desired.